Paper product with chemical watermark and means for making same



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United States Patent "ice 3,140,959 PAPER PRGDUCT WITH Ci-EMHQAL WATER- MARK AND MEANS FOR MAKING SAh [E Frans V. E. Vaurio, Appleton, Wis, assign'or by mesne assignments, to Customark Corporation, Appleton,

Wis., a corporation of Wisconsin No Drawing. Filed Dec. 27, 1960, Ser. No. 7S,223

8 Claims. (Cl. 11738) This invention relates to a paper sheet product with a chemical watermark and means for making same. More in particular this invention relates to means for forming a chemical watermark in otherwise finished paper sheet products which simulates well known watermarked paper sheet products.

Particularly in office operations of commercial enterprises it is often desirable to have Writing stationery and other forms of business and professional papers watermarked. Oftentimes business trademarks are watermarked for identity and protective purposes and such water-marking serves as an additional means of distinctiveness associated with a particular business enterprise.

The present practice of watermarking is usually performed during the paper-making process by providing rolls with raised designs interposed usually at a point before the wet paper Web enters the dryers. The fibers in the web are displaced in horizontal position and the paper is thus rendered thinner and consequently more transparent in the area of the watermark when viewed under transmitted light. Thus the embossed rolls form the configuration or design of the mark in the damp or wet paper which upon drying remains permanent. After the papermaking and watermarking process is complete the finished paper is cut into sheets of various sizes, such as those established for stationery and the like.

Another known method of forming a watermark involves the employment of a band fitted about a roll and carrying the design or configuration of the water mark in relief. The design of the mark in relief on the band is brought into contact with the wet paper web at the wet presses beyond the Fourdrinier or wet end. At that point the paper is still plastic and compresses readily. The resulting compression of fibres, reducing entrapped air and light refraction, increases the transparency in the area conforming to the configuration of the watermark.

Watermarked paper made as above described has several disadvantages. First the commercial paper making machines are very large and produce paper at a high volume rate. Thus for economical reasons a customer desiring paper bearing a private watermark such as a trademark must purchase a large amount of each kind of paper needed. This of course limits such privately watermarked papers to few but relatively large industrial users or governmental departments as it is obvious that smaller enterprises could not economically purchase and stock a supply sufficient for several years. econd, the cost of the embossed or banded rolls for the paper making machine is obviously extremely high and could therefore not be afforded by smaller industrial users. Third, the cost of setting up the embossed or banded rolls involves both labor as Well as loss of production on the paper making machinery which must be taken into account in the net cost to the purchaser. Furthermore, among other disadvantages, the purchaser finds that his private watermark is not positioned uniformly in the finished cut stationery unless he assumes the adidtional labor cost and paper waste involved in constantly positioning relatively the rolled paper and the cut-off knife. While private Watermarks may be formed by presently known methods, it is 3,14%,959 Patented July 14, 1964 thus clear that orders for paper products so marked must be large if the cost thereof is to be economically justified and orders in small quantities are of such high cost as to be rarely justified.

The present invention contemplates the elimination of the above mentioned disadvantages. It is therefore one object of this invention to convert blank paper sheet into a paper sheet product having a uniformly positioned chemical watermark therein conforming to a selected design.

Another object of this invention is to form in a blank cut sheet paper product a visible chemical watermark confroming to a selected design.

A further object of this invention is to form a chemical watermark by impregnating blank paper in the area of the configuration of the mark with a substantially colorless curable thermosetting resin which may or may not be followed by curing the resin.

A still further object of the present invention is to form a chemical watermark according to the preceding objects, wherein the cured resin forming the mark is insoluble in water and ordinary organic solvents.

A yet further object of this invention is to provide blank paper intended for use as paper sheet products with a chemical watermark, according to the preceding objects, wherein the mark may conveniently be positioned uniformly on all sheets.

Another object of this invention is to provide such paper with a chemical watermark, according to the preceding objects, in small quantities at low cost.

Another object of this invention is to provide a method of forming a chemical watermark in paper involving the adequate displacement of entrained air within and be tween the fibers of the paper.

Another object of the invention is to provide a method of forming a chemical watermark by replacing air entrained in a paper sheet product with a material having an index of refraction reasonably close to that of cellulose.

Another object of the invention is to provide a method of forming a chemical watermarked paper sheet product by impregnation thereof within the area of configuration of said mark to replace entrapped air in the area with a substantially colorless thermosetting material curable to insoluble resin at room temperature.

These and other desirable objects inherent in and encompassed by the invention will be more readily understood from the ensuing description and the appended claims.

In my previous application for patent filed on August 7, 1959, Serial No. 832,148, now Patent No. 3,085,898, of which this application is a continuation-in-part, there is described numerous novel chemical compositions and method for impregnating blank paper sheet products in the area of the configuration of a selected mark to obtain a simulated watermark. However none of the chemical compositions there described underwent chemical change by reaction. The simulated watermarks thus obtained possessed all the required properties found in watel-marks and are essentially permanent in character except that the marks are not resistant to solvent action. Sometimes inks contain solvents which would attack the mark and thus affect adversely its distinctiveness.

In the present invention the compositions employed may chemically react to form substantially colorless cured resins which are essentially insoluble in ordinary or common solvents and thus the mark is resistant to solvent action. Thus the major difference between the present application and my above mentioned prior application is the employment of impregnating compositions arsoess C which are chemically reactive to form insoluble resins instead of chemically unreactive compositions for use in providing blank paper with a chemical watermark.

The term chemical watermark in paper products as herein employed is intended to mean a mark of selected design wherein the area within the configuration of the mark is impregnated with a chemical composition accord ing to this invention resulting in a mark on the paper which substantially meets all of the requirements possessed by a watermark made by the well-known watermarking process. Thus to the consumer the chemical watermark of this invention is indistinguishable from the well known watermark. However since this discussion is directed to those skilled in the art as distinct for the general public the term chemical watermark is used to distinguish the marks obtained according to this invention from the marks obtained by means of the known watermarking methods.

According to this invention blank paper (i.e., having no watermark) is provided with a chemical watermark by impregnating the area of configuration with a novel liquid composition of this invention whereby after curing the liquid resin of the composition to solid, transparent or translucent areas are created in the paper sheet conforming to the desired configuration of the mark. The resulting chemical watermark possesses for all practical purposes the same general physical characteristics in use as a watermark formed by the known processes previously described.

A chemical composition suitable for forming a chemical Watermark as above mentioned must have the ability to mark the paper in a manner to render it more translucent or substantially transparent in the impregnated area. Further the chemical composition employed to form the chemical watermark should not alter the surface of the paper adversely. For example it must not render the surface glossy in the impregnated area and must not alter the erasability characteristic of the paper. In addition the chemical composition must withstand aging without substantial discoloration and must not become indistinct through slow migration of the chemicals or otherwise. And of course, the area within the chemical Watermark must accept typing, pencilling, printing and writing inks without adverse effects such as feathering or skipping. Certain chemical compositions of this invention have been successfully employed in the formation of chemical watermarks which conform to the above mentioned requirements as hereinafter described.

A conventional watermark, from a fundamental viewpoint, possesses a translucency of higher degree in the area of the mark than that possessed by the paper in the unmarked areas. The most common type of conventional watermark appears more transparent than the surrounding unmarked paper when viewed under transmitted light.

After considerable experimental work it was discovered that soluble resin compositions which were capable of being cured at substantially room temperatures (57, 70- 90 F.) into insoluble colorless resinous products can be successfully employed to form excellent pseudo-Watermarks which possess all of the desired characteristics of watermarks made according to conventional processes. Because a chemical watermark must necessarily be essentially colorless the resin composition must be substantially colorless which requirement precludes the use of many known resins.

Broadly speaking a substantially colorless solution of a curable liquid resin in an organic solvent wherein the resin is curable to a substantially insoluble colorless state rapidly by hardening agents (curing promoters) which may be added to the resin solution provided that the cured resins obtained with the aid of hardening agents remains substantially colorless. Commercial sources of some liquid resins including trade names and manufacturers which were found satisfactory for this invention are shown in Table I below.

TABLE I Trade Name Type Manufacturer Epon 812. Shell Chemical 00. Dow D.E. Dow Chemical Co. Dow D.E R (361 Do. Dow D.E.R 664 D0.

Dow D.E.R: 667

Do. Marblette Corp.

Ureatormaldehyde. Crest Chemical Corp. Crestoset MFL. do Do. Oxiron 2002 Food Machinery and Chemical Corp.

All of the resins in Table I are of the thermosetting type. However, it is understood that the two Paraplex resins are of the polyester type; the Epiphen resin is understood to be of the phenol formaldehyde modified epoxy type; the two Crestoset resins are understood to be of the modified urea formaldehyde type and the remaining resins are understood to be of the epoxy class.

Known methods for preparation of epoxy type resins are numerous as shown, for example, in US. Patents Nos. 2,444,333; 2,503,726; 2,575,558; 2,582,985; 2,585,115; 2,592,560; 2,694,694; 2,712,535 and 2,864,775. One method for manufacturing an epoxy type resin suitable for use in this invention is the soluble resinous product of the reaction between Bisphenol A (4,4' isopropylidine diphenol) and epichlorohydrin as indicated below.

The epichlorohydrin and Bisphenol A, usually in a molar proportion of about 10:1, respectively, are placed in a distilling flask, provided with a stirrer and temperature control means, and the flask placed in an inert gas atmosphere such as nitrogen. A reaction period of about 120150 hours at about 30-50" C. is maintained after which period the temperature is raised to about 80-100 C. and the pressure reduced for the purpose of removing excess epichlorohydrin. The residual intermediate product thus formed is then dissolved in an organic solvent, such as toluene, and an aqueous solution of an inorganic hydroxide (e.g., NaOH) is added slowly with agitation. The amount of inorganic hydroxide added should be slightly in excess of the stoichiometric equivalent to the chlorine present. The resulting mixture is stirred until the reaction is substantially complete. The resinous mass thus obtained is washed with distilled water to remove the inorganic chloride salt formed and excess inorganic hydroxide. The water is then removed by distillation and the residue is a colorless, clear epoxy type liquid resin which is diglycidyl ether of Bisphenol A. The resin thus obtained is a mixture of component compounds having an average molecular weight of about 340-350 may be employed to form chemical watermarks acc0rdand conforming to the following formula:

ing to this invention. Such resins might be cured more where 11 is zero to about 20 or more.

6 However it will be apparent from the average mothis invention. Thus the closer the index of refraction lecular weight of about 3404,50 that the major proporof the resin employed is to the index of refraction of the tion of the resin obtained conforms to the above formula cellulose, paper the greater amount of parallel light can when n equals zero. The epoxy resin obtained has an pass through the paper in the impregnated areas of the epoxide equivalent weight of about 173-179 and is cur- 5 chemical watermark which porperty (i.e., transparency) is able as explained later herein. most desirable. Conversely the greater the difference be- The term epoxide equivalent weight means the weight tween the indexes of refraction results in a corresponding in grams of resin containing one gram equivalent of greater amount of diffusion of light. From this it is apepoxide. It is usually (but not necessarily) about 0neparent that if the difference in the indexes of refraction half the average molecular weight as most of these resins 10 is large the resulting chemical watermark is faint and are diepoxides. may be perceived by the eye with difiiculty which of course In the case of Dow D.E.R. 667 epoxy resin the value may n t e satisfactory- In all of the examples shown of n in the above formula apparently is appreciably above later herein as well as Table I the resins employed poszero as the average molecular weight of thi resin i sessed an index of refraction between 1.4 and 1.7. in th range of 3200-4000, Although several types of thermosetting resins of Table The chemical structure or preparation of most of these I and the resins 0f the P in the p e hereproprietary resins apparently are in the nature of trade in Were Capable of Producing good Psuede-watemafks secrets and thus not available. However it is believed fleeeiding t nti n it Was bserved that the resins that one or more of the epoxy type resins in Table I are of the P Y Class Were Somewhat Superior for (this P essentially diglycidal ether of para, para-isopropylidene- 2Q P than i other YP The P Y resins are known to diphenol also known as diglycidal ether of Bisphenol A have the eblllty 9 P e l P y from e er e formed by reacting epichlorohydrin and Bisphenol A and effects due to aging which 18 P y due {0 then ablllty having the fouowing structural f l to react with acid materials. Further, epoxy type resins 0 CH3 0 generally do not possess any part cularly obnoxious odors g] as compared with some other resins. OH -OI-Io- Accelerated curing of resins of the type indicated in km Table I can be effected conveniently by compounds known The Epoxide 201 resin is believed to be a diepoxide in the trade as hardeners SL161) that the resinswill cure rived from peracetic acid, known as 3,4-epoxy-6-methylat room temperatilres (7 90 m tune" For cyclohexylmethyl 3,4 epoxy 6 methylcyclohgxane 3O purposes of the present invention the cure time for these carboxylate of the following structural formula. Tesins may be as long as two i sun qmte satisfactory. Thus short cure time is not necessarily re- H H2 H H H quired in this invention. Generally speaking the hard- O0C eners may be classed as curing agents but not neces- 0 0 sarily catalyst-s. Strictly speaking a true catalyst is not 3 3 7 chemically combined with the cured resin as distinct from H H H H H2 H a compound which accelerates curing but also becomes Mamglas 655 is believed to be an epoxy resin made by chemically combined with the cured resin. Both types condensing epichlorohydrin and Bisphenol however, are referred to as curing agents" becau se they Th Epiphen ER 823 resin is believed to be a phenolaccelerate the curing rate. In the present invention nu- .formaldehyde novolac resin and epichlorohydrin condeneurlng agents of hardeners e p y Wlth sation product of the following structure: succcessful results. Some of these curing agents found 0 urn-on-omoomorro1n JOHZO Q I O Q on.

Diepoxide AG-13E is understood to be bis-epoxydito be satisfactory are shown in Table II by their comcyclopentyl ether of ethylene glycol. Epo l 741 i b mercially available trade names and manufacturers. lieved to be epoxidized soybean oil further described in TABLE II US. Patent No. 2,919,283.

Oxiron 2 00 2 is understood to be an epoxidized poly- T d N M I t olefin prepared in accordance with US. Patents Nos. m 6 mm 1 auu ac um 2,326,556; 2,833,747; 2,329,131 and versamid 115 General M1115 Corporation Aside from the fact that the resin employed must be B32: 3-52% %D- g g: gggggg-g DOWDEIIQmiCaICOIHpaHY- Substantially Colorless f i g p -W rm rk shenH 21 f; sheuc'hemicaloompwy Rohm and Haas Co.

MarBlette Corp.

Shell Chemical Co. Harshaw Chemical Comaccording to this invention it must also posses an index DMP"30 5 Maraset H655. of refraction within critical limits of 1.4 to 1.7 inclusive lgg ag s t lisss and the preferred range of limits is 1.45 to 1.65 as T I measured at 25 by conventlonal the N-Aminoethyl Piperazine J'efiersdn Chemical Comwell known Abbe refractometer. Th1s is predicated on pany,Ine.

the fact that the index of refraction of most cellulose is Versamid125" ggggf ggg g 1.53-1.55, as obtained by comparison with various organic ERL 2807.- Bakelite Corp.

Hardener 951 CIBA Company, Inc. fluids measured by an Abbe refractometer, and it is de- Hammer EC Bergen Chemical sidable to employ a resin having an index of refraction g gg Q ggl i e cg gll efi csl Corp. reasonably close to that of the cellulose of the paper to H xahydro hthane Auhydride Allied Chemical Corp.

which the chemical watermark is applied according to Similar as the case of the proprietary resins of Table I most of the chemical formulations for the curing agents of Table II are not available. The Dow D.E.R. Exp. Resin X-2654.4 is believed to be a polyamine. BF -4OO is understood to be a complex of boron fluoride with monoethylamine. Eporal is understood to be 4,4'-diaminodiphenyl sulfone. Maraset H655 is characterized as a tertiary amine. The DMP- is understood to be 2,4,6- tri(dimethyl aminoethyl) phenol. Other curing agents for epoxy resins found to be satisfactory include diethylene triamine, pyromellitic dianhydride, N-arnino ethyl piperazine, methyl nadic anhydride, trimellitic anhydride, dibutyl tin maleate, nadic anhydride, diethylene triamine, diphenyl phosphite, N-acetylethanolamine and dipropylene triamine.

All of the curing agents shown in Table II were found suitable for epoxy type resins of Table I except that Cadox MDP is for polyester type resins.

There are numerous known curing agents (hardeners) for epoxy type resins which are described in publications such as Epoxy Resin by Skeist (1958), published by Reinhold, New York; High Polymers, vol. X, Schildknecht (1956), published by Interscience, New York; Epoxy Resins, by Lee and Neville (1957), published by McGraw-Hill, New York; and U8. Patents Nos. 2,510,885; 2,548,447 and 2,643,239. In general, polyamines such as diethylenetriaminc, triethylenetetramine and xylylenediamine are good curing agents for epoxy type resins. It will be seen from the examples shown herein that the amount of hardener may range from as little as 0.2 percent to as high as about 60 percent by weight Where a solvent is not employed and as low as 0.2 percent to as high as about 30 percent by Weight when a solvent is employed.

Curing agents found satisfactory for the urea formaldehyde and melamine formaldehyde resins of Table l include maleic anhydride, citric acid, n-butyl acid phosphate, chloroacetic acid, dichloroacetic acid, oxalic acid, monon-butyl orthophosphate, sulfamic acid and glacial acetic acid.

In some instances a resin of Table I with or without a curing agent could be satisfactorily used directly to make a chemical watermark according to this invention. However for the most part better results could be obtained if a suitable organic solvent was used with the resin. The solvent employed must, in addition to being a solvent for the resin used, be essentially colorless, non-corrosive to paper, possess a vapor pressure at room temperatures high enough to evaporate with a sutficent rapidity to prevent migration of the resin in paper, possess a vapor pressure low enough to carry the resin into the paper (penetration) prior to evaporation, and, lastly, chemically inert under the conditions employed in this invention.

The solvent preferably should be of the polar type as it appeared that wetting of the paper fibers was better than in the case of non-polar solvents although nonpolar solvents can be used as will be seen later. The solvent also must be compatible with the resin seiected. If the viscosity of the solution is too low the penetration into the paper is too rapid causing the chemical watermark to be blurred or indistinct. On the other hand if the viscosity of the solution is too high the penetration into the paper is poor and a substantial portion of the resin is deposited on the surface of the paper sheet resulting in a chemical watermark which may have a glossy surface. This is not only undesirable in appearance but may be adversely sensitive to inks. In such case writing inks, for example, do not adhere to the resin surface resulting in skipping as is known in the trade. Excessive penetration into the paper results in migration of the resin which tends to make a chemical watermark blurred or indistinct. Table III below lists many solvents which were found to be satisfactory for this invention.

TABLE III Name:

Methylisobutylketone Ethyl lactate Ethyleneglycol monomethyl ether Ethyleneglycol dimethyl ether Ethyleneglycol monoethyl ether Ethyleneglycol diethyl ether Ethyleneglycol monobutyl ether Ethyleneglycol monohexyl ether Dibutyl phthalate Diethyleneglycol monomethyl ether Diethyleneglycol monoethyl ether Diethyleneglycol monobutyl ether Diethyleneglycol diethyl ether Dimethyl formamide Diemethyl sulfoxide Triacetin Ethyleneglycol monoethylether acetate N-Butyl acetate, Diethyleneglycol monoethylether acetate Cyclohexanone in order to evaluate the various compositions of this invention, chemical watermarks of excellent quality were obtained in the laboratory by hand impregnation. The hand impregnation was accomplished by depositing a small metered amount (e.g., l to 2 grams) of the composition on the surface of a foot-square piece of onequarter inch thick plate glass. The liquid composition was spread uniformly over the glass surface with a conventional handproofer consisting of an engraved roll bearing 75 depressions per inch and fitted with a handle. A die or hand stamp of rubber-like material having inscribed in relief on the face thereof a design or configuration conforming to a typical Watermark was pressed against the wet film of the composition and then stamped on the paper sheet. The chemical watermarked paper sheet was allowed to dry and cure at ambient room temperatures (7090 F.) and then examined. Thus chemical watermarks were applied to paper sheets much in the same manner as one would rubber stamp paper using an inked pad except instead of ink the compositions of this invention were used.

Where curing agents were employed the time required for the resin to cure at ambient room temperatures to a degree sufiicient to resist solubility in ethanol or acetone varied somewhat depending on the particular resin used. However all resins with curing agents of the compositions employed in the various examples shown later herein cured satisfactorily with reference to ethanol or acetone solubility in periods less than two weeks at ambient room temperatures.

Testing for cure of the resin in the chemical watermark made by laboratory hand stamping as above described was made by agitating the paper sheet bearing the chemical watermark in the solvent (e.g., ethanol) for a period of two minutes at room temperature. If the solvent extracted resin the chemical watermark disappeared. Where, on the other hand, the chemical watermark remained after agitation in the solvent this indicated that the resin cured to a solvent resistant state.

The two week curing time requirement is generally not objectionable because packing and shipping operations for paper stationery together with upacking and use by the customer usually is at least this long. Of course if desired the curing rate of the resin can be greatly accelerated by heating the chemical watermarked paper to 7090 C. for a period of about one hour without discoloring the paper.

By way of illustration of the invention, excellent chemical watermarks were obtained by laboratory hand impregnation, as above described, employing novel compositions of this invention in each of the following examples, the stated proportions being in terms of weight.

Example 1 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Ethyleneglycol monomethyl ether 108 grams, 60%.

Example 2 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%.

Ethyleneglycol monomethyl ether Diethyleneglycol monoethyl ether Example 6 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7 Diethyleneglycol diethyl ether 108 grams, 60%.

Example 7 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%.

Diethyleneglycol diethyl ether Example 8 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12) grams, 7%. Diethyleneglycol monobutyl ether 108 grams, 60%.

Example 9 Dow D.E.R. 332 100 grams, 58%.

Dow Hardener X2654.4 Diethyleneglycol monobutyl ether Example 10 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X-2654.4 12 grams, 7%. Ethyleneglycol monoethylether acetate 108 grams, 60%.

Example 11 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%.

Ethyleneglycol monoethylether acetate 51.4 grams, 30%.

Example 12 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Methyl isobutyl ketone 108 grams, 60%.

Example 13 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%. Methyl isobutyl ketone 51.4 grams, 30%.

Example 14 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Dimethyl formarnide 108 grams, 60%.

Example 15 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 grams, 12%. Dimethyl formamide 51.4 grams, 30%.

51.4 grams, 30%.

51.4 grams, 30%.

51.4 grams, 30%.

20 grams, 12%. 51.4 grams, 30%.

10 Example 16 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Dimethyl sulfoxide 108 grams, 60%. Example 17 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%. Dimethyl sulfoxide 51.4 grams, 30%.

Example 18 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Ethyleneglycol monoethyl ether '108 grams, 60%.

Example 19 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%. Ethyleneglycol monoethyl ether 51.4 grams, 30%.

Example 20 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Ethyleneglycol monomethyl ether 108 grams, 60%.

Example 21 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%. Ethyleneglycol monomethyl ether 51.4 grams, 30%.

Example 22 Dow D.E.R. 332 60 grams, 33%. Dow Hardener X2654.4 12 grams, 7%. Ethyleneglycol monobutyl ether 108 grams, 60%.

Example 23 Dow D.E.R. 332 100 grams, 58%. Dow Hardener X2654.4 20 grams, 12%.

Ethyleneglycol monobutyl ether 51.4 grams, 30%.

Ethyleneglycol monohexyl ether 51.4 grams, 30%.

The foregoing examples illustrates the wide range of solvent content in the compositions which can be satisfactorily employed. In some instances a solvent was omitted with satisfactory results as shown later herein and in other instances a solvent concentration as high as produced satisfactory results. Of course in commercial operations the particular solvent used and content thereof in the composition for best results will depend to some extent on the type of commercial printing press used and conditions of operation as well as the characteristics of the paper to which a chemical watermark is to be imprinted in accordance with this invention.

The following immediate group of examples illustrates several compositions all of which produced excellent chemical watermarks according to this invention. Some of these compositions have been employed using commercial printing machinery and in each case excellent chemical watermarks were obtained.

Diethyleneglycol monomethyl ether 14.3

1. Example 27 Percent Dow D.E.R. 332 (resin) 44.5 Dow Hardener X2654.4 11.0 Diethyleneglycol nionornethyl ether 44.5

Example 28 Dow D.E.R. 332 (resin) 40.0 Dow Hardener X2654.4 20.0 Diethyleneglycol monornethyl ether 40.0

Example 29 Dow D.E.R. 332 (resin) 33.4 Dow Hardener X2654.4 33.3 Diethyleneglycol monomethyl ether 33.3

Example 30 Maraglas 655 (resin) 40.0 Dow Hardener X2654.4 20.0 Diethyleneglycol monomethyl ether 40.0

Example 31 Maraglas 655 (resin) 66.7 Shell H2 (hardener) 33.3

Example 32 Epon 812 (resin) 50.0 Shell H2 (hardener) 50.0

Example 33 Epon 812 (resin) 40.0 Dow Hardener X2654.4 20.0 Diethyleneglycol monornethyl ether 40.0

Example 34 Epon 812 (resin) 33.4 Dow Hardener X2654.4 33.3 Diethyleneglycol monornethyl ether 33.3

Example 35 Epon 812 (resin) 90.9 DMP-30 9.1

Example 36 Dow D.E.R. 332 (resin) 65.6 Ethylene triarnine (hardener) 1.6 Diethyleneglycol monornethyl ether 32.8

Example 37 Dow D.E.R. 332 41.7 Dow Hardener X2654.4 16.6 Diethyleneglycol monomethyl ether 41.7

Example 38 Dow D.E.R. 332 (resin) 43.5 Dow Hardener X2654.4 13.0 Diethyleneglycol monomethyl ether 43.5

Example 39 Dow D.E.R. 332 (resin) 45.5 Dow Hardener X2654.4 9.0 Diethyleneglycol monornethyl ether 45.5

Example 40 Dow D.E.R. 332 (resin) 47.6 Dow Hardener X2654.4 Diethyleneglycol monomethyl ether 47.6

Example 41 Dow D.E.R. 332 (resin) 40.0 Pyromellitic anhydride (hardener) 20.0 Diethyleneglycol monomethyl ether 40.0

Example 42 Parez 607 (resin) 33.3 Diethyleneglycol monomethyl ether 66.7

Example 43 Percent Dow D.E.R. 332 (resin) 49.9

Dow Hardener X2654.4 0.2

Diethyleneglycol monomethyl ether 49.9

Example 44 Dow D.E.R. 332 (resin) 48.9

Dow Hardener X2654.4 2.2

Diethyleneglycol rnonornethyl ether 48.9

Example 45 ERL 2795 (resin) 99.5

ERL 2807 (hardener) 0.5

Example 46 ERL 2795 (resin) 97.6

ERL 2807 (hardener) 2.4

Example 47 ERL 2795 (resin) 95.2

ERL 2807 (hardener) 4.8

Example 48 Maraglas 655 (resin) 57.4

Dow Hardener X2654.4 14.4

Diethyleneglycol monomethyl ether 28.2

Example 49 Maraglas 655 (resin) 44.5

Dow Hardener X2654.4 11.0

Diethyleneglycol monornethyl ether 44.5

Example 50 Maraglas 655 (resin) 99.0

Shell Hl (hardener) 1.0

Example 51 Maraglas 655 (resin) 48.8

Shell Hl (hardener) 2.4

Diethyleneglycol monomethyl ether 48.8

Example 52 Maraglas 655 (resin) 62.6

Shell Hl (hardener) 6.2

Diethyleneglycol monomethyl ether 31.2

Example 53 Maraglas 655 (resin) 50.0

Shell Hl (hardener) 25.0

Diethyleneglycol monomethyl ether 25.0

Example 54 Maraglas 655 (resin) 64.6

Shell H2 (hardener) 3.2

Diethyleneglycol monornethyl ether 32.2

Example 55 Maraglas 655 (resin) 62.6

Shell H2 (hardener) 6.2

Diethyleneglycol monomethyl ether 31.2

Example 56 Maraglas 655 (resin) 50.0

Shell H2 25.0

Diethyleneglycol monomethyl ether 25.0

Example 57 Epon 812 (resin) 66.7

Shell H2 (hardener) 33.3

Example 58 Epon 812 (resin) 45.4

Dow Hardener X2654.4 9.2

Diethyleneglycol monomethyl ether 45.4

r 13 Example 59 Percent Epon 812 (resin) 40.0 Dow Hardener X2654.4 20.0 Diethyleneglycol monomethyl ether 40.0

Example 60 Epon 812 (resin) 95.2 DMP 30 (hardener) 4.8

Example 61 Epon 812 (resin) 83.3 DMP 30 (hardener) 16.7

Example 62 Araldite 502 (resin) 74.1 Hardener 951 7.4 Diethyleneglycol monomethyl ether 18.5

Example 63 Epiphen ER-823 (resin) 45.5 Hardener EC-20 9.0 Diethyleneglycol monomethyl ether 45.5

Example 64 Parez 613 (resin) 30.4 Dow D.E.R. 332 (resin) 21.9 Dow Hardener X2654.4 10.9 Chloroacetic acid (hardener) 2.2 Diethyleneglycol monomethyl ether 34.6

Example 65 Dow D.E.R. 332 (resin) 2 50 Methyl nadic anhydride 50 I Example 66 Dow D.E.R. 332 (resin) 41.6 Methyl nadic anhydride 58.4

Example 67 Dow D.E.R. 332 (resin) 33.3 Methyl nadic anhydride 66.7

Example 68 Dow D.E.R. 332 (resin) 48.1 BF 400 (hardener) 3.8 Methyl nadic anhydride 48.1

Example 69 Maraglas 655 (resin) 93.0 Maraset Hardener H555 7.0

' Example 70 Maraglas 655 (resin) a 90.9 Maraset Hardener H555 9.1

Example 71 Maraglas 655 (resin) 77 'Maraset Hardener H555 23 Example 72 Maraglas 655 (resin) 50 Maraset Hardener H555 50 Example 73 Dow D.E.R. 332 (resin) 47- Pyrornellitic anhydride 4.8 Diethyleneglycol monomethyl ether 47.6 Example 74 Dow D.E.R. 332 (resin) 4O Pyromellitic anhydride 20 Diethyleneglycol monomethyl ether 40 Example 75 Dow D.E.R. 332 (resin) 56 BP -400 4 Diethyleneglycol monomethyl ether 4O Example 76 Percent Dow D.E.R. 332 (resin) 69 N-Arninoethyl Piperazine 10 Diethyleneglycol monomethyl ether 21 Example 77 Dow D.E.R. 332 (resin) 72 N-Arninoethyl Piperazine 7 Diethyleneglycol monomethyl ether 21 Example 78 Dow D.E.R. 332 (resin) 66.7

N-Aminoethyl Piperazine 13.3

Diethyleneglycol monomethyl ether 20.0

Example 79 Dow D.E.R. 332 (resin) 64.6

N-Aminoethyl Piperazine 16.1

Diethyleneglycol monomethyl ether 19.3

Example 80 Dow D.E.R. 3'32 (resin) 45.5

Eporal (hardener) 9.0

Diethyleneglycol monomethyl ether 45 .5

Example 81 Dow D.E.R. 332 (resin) 40 Eporal (hardener) 20 Diethyleneglycol monomethyl ether 40 Example 82 Dow D.E.R. 332 (resin) 58.6

BF -Phenol Complex (hardener) 0.3

Diethyleneglycol monomethyl ether 41.1

Example 83 Dow D.E.R. 332 (resin) 35.5

Hexahydrophthalic Anhydride (hardener) 28.8

BF -Phenol Complex (hardener) 0.2

Diethyleneglycol monomethyl ether 35.5

Example 84 Dow D.E.R. 332 (resin) 41.5

Hexahydrophthalic Anhydride (hardener) 16.7

BFg-Phenol Complex (hardener) 0.3

Diethyleneglycol monomethyl ether 41.5

Example 85 Dow D.E.R. 332 (resin) 45.3

BFg-Phenol Complex (hardener) 0.3

Hexahydrophthalic Anhydride (hardener) 9.1

Diethyleneglycol monomethyl ether 45.3

Example 86 Dow D.E.R. 332 (resin) 58.6

BF -Piperidine Complex (hardener) 0.3

Diethyleneglycol monomethyl ether 41.1

Example 87 Dow D.E.R. 332 (resin) 58.5

BF -Piperidine Complex (hardener) 0.6

Diethyleneglycol monomethyl ether 40.9

Example 88 Dow D.E.R. 332 (resin) 58.3

BF -Piperidine Complex (hardener) 0.9

Diethyleneglycol monomethyl ether 40.8

v Example 89 Dow D.E.R. 332 (resin) 57.8

B'F -Piperidine Complex (hardener) 1.7

Diethyleneglycol monomethyl ether 40.5

Example 90 Dow D.E.R. 332 (resin) 55.6

BF -Piperidine Complex (hardener) 5.6

Diethyleneglycol monomethyl ether 38.8

1 In the preceding five examples the BF -Piperidine Complex is commercially available but may be prepared by bubbling boron trifluoride in piperidine at room temperature.

Example 91 5 Percent Dow D.E.R. 332 (resin) 58.3 BF henol Complex (hardener) 0.8 Diethyleneglycol monomethyl ether 40.9

Example 92 Dow D.E.R. 332 (resin) 58.2 El -Phenol Complex (hardener) 1.2 Diethyleneglycol monomethyl ether 40.6

Example 93 Dow D.E.R. 332 (resin) 33 Crestoset M (resin) 33 BF -Phenol Complex (hardener) 1 Diethyleneglycolmonomethyl ether 33 Example 94 Dow D.E.R. 661 (resin) 29.6 Dow D.E.R. X2673.2 (hardener) 7.4 N-Aminoethyl Piperazine 3.0 Diethyleneglycol monomethyl ether 60.0

Example 95 Dow D.E.R. 664 (resin) 29.6 Dow D.E.R. X2673.2 (hardener) 7.4 N-Aminoethyl Piperazine 3.0 Diethyleneglycol monomethyl ether 60 .0

Example 96 Dow D.E.R. 667 (resin) 29.6 Dow D.E.R. X-2673.2 (hardener) 7.4 N-Aminoethyl Piperazine 3.0 Diethyleneglycol monomethyl ether 60.0

Example 97 Crestoset M (resin) 50 Oxalic acid (hardener) 5 Diethyleneglycol monomethyl ether Example 98 Crestoset M (resin) 45 Oxalic acid (hardener) 5 Diethyleneglycol monobutyl ether 45 Example 99 Crestoset M (resin) 50 50 Oxalic acid (hardener) 5 Diacetin 45 Example 100 Crestoset M (resin) 50 Oxalic acid (hardener) 5 Monacetin 45 Example 101 Crestoset M (resin) 50 Oxalic acid (hardener) 5 Dipropyleneglycol 45 Example 102 Crestoset M (resin) 50 Citric acid (hardener) 5 Diethyleneglycol monomethyl ether 45 Example 103 Crestoset M (resin) 50 Citric acid (hardener) 5 Diethyleneglycol monobutyl ether 45 Example 104 Crestoset M (resin) 50 Citric acid (hardener) 5 Diacetin 45 1 5 Example 105 Percent Crestoset M (resin) 50 Citric acid 5 Monacetin 45 Example 106 Crestoset M (resin) 50 Citric acid 5 Dipropyleneglycol 45 Example 107 Crestoset M (resin) 38.4 Phosphoric acid 3.8 Diethyleneglycol monomethyl ether 57.8

Example 108 Crestoset M (resin) 62.5 Citric acid (hardener) 6.2 Diethyleneglycol monomethyl ether 31.3

Example 109 Crestoset M (resin) 43.4 Citric acid (hardener) 4.3 Diacetin 52.3

Example 110 Crestoset M (resin) 56.2 Citric acid (hardener) 5.6 Monacetin 38.2

Example 111 Crestoset M (resin) 43.4 Citric acid (hardener) 4.3 Dipropylene glycol 52.3

Example 112 Crestoset M (resin) 5O Oxalic acid 5 Ethyleneglycol monohexyl ether 45 In all of the preceding examples a curing agent (hardener) was employed to cure the resin but in some instances a solvent was omitted. As mentioned previously a solvent is not always required. Some of the resins require the presence of a solvent and the amount of solvent employed is governed to an appreciable extent by the impregnating characteristics of the paper to be chemical watermarked in accordance with this invention.

In the following examples a curing agent is omitted. The resin will not cure on contact with the air at ambient temperature. However where curing is desired in the case of chemical watermarking according to this invention the time required to cure the resin to an organic solvent resistant state is not too important for, as previously mentiond, a period of two or more weeks usually elapses between chemical watermarking and the time when the customer receives the product. Thus the following examples illustrate compositions which use results in excellent chemical watermarks according to this invention without employing curing agents.

Example 113 Percent Dow D.E.R. 332 (resin) 65 Diethyleneglycol monomethyl ether 35 Example 114 DOW D.E.R. 332 (resin) 80 Diethyleneglycol monomethyl ether 20 Example 115 DOW D.E.R. 332 (resin) 30 Cyclohexanone 70 Example 116 DOW D.E.R. 332 (resin) 80 Cyclohexanone 20 Example 117 Percent Dow D.E.R. 332 (resin) 80 Monoacetin 20 Example 118 Dow D.E.R. 332 (resin) 80 Diacetin 20 Example 119 Dow D.E.R 332 (resin) 30 Triacetin 70 Example 120 Dow D.E.R. 332 (resin) 8O Diethyleneglycol monohexyl ether 20 Example 121 Dow D.E.R. 332 (resin) 9O Dimethyl sulfoxide Example 122 Dow D.E.R. 332 (resin) 80 Dibutyl phthalate 20 Example 123 Dow D.E.R. 332 (resin) 40 Diethyleneglycol monobutyl ether 60 Example 124 Dow D.E.R. 332 (resin) 40 Dimethyl formamide 60 7 Example 125 Dow D.E.R. 332 (resin) 8O Dimethyl formamide 20 Example 1 26 Dow D.E.R. 332 (resin) 50 Ethyleneglycol monobutyl ether 50 Example 127 Dow D.E.R. 332 (resin) 80 Ethyleneglycol monobutyl ether 20 Example 128 Dow D.E.R. 332 (resin) 3O Ethyleneglycol monoethyl ether 70 Example 129 Dow D.E.R. 332 (resin) 90 Ethyleneglycol monoethyl ether 10 Example 130 Dow D.E.R. 332 (resin) 80 Ethyleneglycol monohexyl ether 20 Example 131 Dow D.E.R. 332 (resin) 30 Ethyleneglycol monomethyl ether 70 Example 132 Dow D.E.R. 332 (resin) 90 Example 135 Dow D.E.R. 332 (resin) 8O Toluene 20 18 Example 136 Percent Dow D.E.R. 332 (resin) 30 Tricresyl phosphate 70 Example 137 Dow D.E.R. 332 (resin) 70 Tricresyl phosphate 30 Example 138 Dow D.E.R. 332 (resin) 30 Xylene 70 Example 139 Dow D.E.R. 332 (resin) Xylene 20 Example 140 Dow D.E.R. 332 (resin) 1 100 Distinetness of the chemical watermark fair-to-good. Not as good as when solvent is present.

Example 141 Crestoset M (resin) 55 Dimethylacetamide 45 Example 142 Dow D.E.R. 667 (resin) 60 Diethyleneglycol monomethyl ether 40 Example 143 Crestoset M (resin) 55 Diacetin 45 Example 144 Crestoset M (resin) 55 Diethyleneglycol monomethyl ether 45 Example 145 Crestoset M (resin) 55 Monacetin 45 Example 146 Crestoset M (resin) 55 Dipropyleneglycol 45 In the above examples it is clear that not only a wide number of solvents can be used but also the proportional amount may range from zero to as high as 80% although the range of 10 to 70% is more preferable. Furthermore some of these compositions are currently used for chemical watermarking paper commercially using conventional printing machinery.

In all of these examples the blank paper product employed in applying the compositions to form chemical watermarks according to this invention was of the bond grade consisting of 25% cotton and 75% woodpulp. The apparent density of the blank paper stock was about 5.0 and its thickness about 4 mils. The resulting chemical watermarks possessed a high degree of transparency. Other types of paper sheet products such as commercial mimeograph, tracing and even newsprint were successfully chemical watermarked with many of these compositions according to the invention.

In the paper industry the terms opaque and semiopaque can refer to varying levels of opacity, depending on the specific type of paper under discussion. For purposes herein, more definite meanings can be given these terms by the following explanation.

In the writing paper field, trade practice classifies an opaque sheet of bond paper as one of a standard weight (500 sheets cut 17 inches by 22 inches, weighing between 19.5 lbs. and 20.5 lbs.) having a TAPPI (Technical Association of the Pulp and Paper Industry) opacity in excess of 87%. This percent is the reciprocal of the transmission of monochromatic light passing through the paper and photometrically measured.

The less commonly used term semi-opaque is generally accepted by the trade as a standard weight sheet of bond paper having a TAPPI opacity somewhere between 87% and 65%.

Writing papers having a TAPPI opacity less than 65 are often referred to as transparent. It will suffice to say that the lower the TAPPI opacity, the more often the trade refers to transparency, and the closer the opacity is to 65%, the more often the trade uses the the term translucent. Translucent papers usually retain the more common characteristics of bond papers, such as formation and brightness, whereas transparent sheets most often have a more uniformly translucent fibre mass with considerably less brightness. This holds true whether the paper under discussion is made entirely of chemical wood pulp, a blend of chemical wood pulp and cotton or linen fibres.

Technically the term translucent usually implies that a ray of light passing through a material is diffused while the term transparent implies that a ray of light passing through is not diffused. Thus a translucent object may vary from opaque to transparent according to the magnitude of diffusion of light passing therethrough. However, for purpose of this discussion the term transparent is used to denote that the magnitude of diffusion of light passing through the paper is not greater than that found in commercial tracing paper. Thus if a sheet of paper possesses a TAPPI opacity of less than 65% it is termed herein as transparent and conversely if 65 or greater it is termed herein as translucent.

It has thus been shown that ordinary grades of stationery can be provided with a chemical watermark by a curable chemical impregnation according to this invention by means of a simple hand method or commercial printing machines. In commercial printing machines the compositions of this invention are employed instead of printing inks and may be applied in a similar manner as that described in my abovementioned co-pending application. From this it can be readily appreciated that small quantities of paper may be provided with a chemical Watermark of selected configuration or design at costs which meet requirements of smaller volume customers and thereby making available, economically, a long sought paper product.

Based on the weight of paper the amount of curable impregnating composition of this invention, in terms of percent by weight, may vary due to the density of the paper and its impregnating characteristics. Therefore a sufficient amount effective to reduce the TAPPI opacity to below 65% is employed when working with translucent paper. In relation to the bond paper used in the examples, an impregnation in the amount of about or less by weight of the resin based on the weight of the paper within the area impregnated gave satisfactory results.

Having thus described several embodiments of the invention it can now be seen that the objects of the invention have been fully achieved and it must be understood that changes and modifications may be made which do not depart from the spirit of the invention nor from the scope thereof as defined in the appended claims.

What is claimed is:

1. A method of imparting a chemical watermark of selected design to a finished sheet of paper which comprises the steps of printing the design on a portion of the surface of said paper sheet with a liquid composition consisting essentially of a synthetic, thermosetting, curable resin and an organic solvent, and removing said solvent to obtain a substantially colorless chemical watermark of said deposited resin having an index of refraction of about 1.4 to about 1.7, and said chemical watermark being substantially free from gloss, having ink receptivity and resisting discoloration with aging substantially in the same way as the paper.

2. A method of imparting a chemical watermark of selected design to a finished sheet of paper which comprises the steps of printing the design on a portion of the surface of said paper sheet with a liquid composition consisting essentially of synthetic, thermosetting curable resin and up to about 60% by weight of a curing agent for said resin, and hardening the composition by curing the resin to obtain a substantially colorless, chemical watermark having an index of refraction of about 1.4 to about 1.7, and said chemical watermark being substantially free from gloss, having ink receptivity, and resisting discoloration with aging in substantially the same way as the paper.

3. A paper article with a chemical watermark which includes, in combination, a paper sheet, a chemical watermark composition applied on said sheet in the configuration of a selected design, the chemical watermarking composition consisting essentially of a hardened, synthetic, thermosetting resin having an index of refraction of about 1.4 to about 1.7, and said chemical watermark being substantially free from gloss, having ink receptivity and resisting discoloration with aging substantially in the same way as the paper.

4. An article as in claim 3 further characterized in that the resin is an epoxy resin.

5. An article as in claim 3 further characterized in that the resin is a melamine formaldehyde resin.

6. An article as in claim 3 further characterized in that the resin is a urea-formaldehyde resin.

7. An article as in claim 3 further characterized in that the resin is a polyester resin.

8. A paper article with a chemical watermark which includes, in combination, a paper sheet, a chemical watermark composition printed on said sheet in the configuration of a selected design, the chemical Watermarking composition consisting essentially of a hardened, synthetic, thermosetting resin having an index of refraction of about 1.4 to about 1.7, and said chemical watermark being substantially free from gloss, having ink receptivity and resisting discoloration with aging substantially in the same way as the paper.

References Cited in the file of this patent UNITED STATES PATENTS 1,479,337 Temple Jan. 1, 1924 1,998,237 Himmell Apr. 16, 1935 2,285,095 Rothrock et a1. June 2, 1942 2,620,316 Ritson Dec. 2, 1952 2,642,390 Garofano June 16, 1953 2,683,089 Reynolds July 6, 1954 2,721,505 Mossberg Oct. 25, 1955 2,872,428 Schroeder Feb. 3, 1959 2,888,452 Schmid et al May 26, 1959 2,900,364 Wasserman Aug. 18, 1959 2,904,447 Hochuli et al Sept. 15, 1959 FOREIGN PATENTS 696,673 Great Britain Dec. 22, 1950 OTHER REFERENCES The Condensed Chemical Dictionary, Reinhold Publishing Corp., Sixth Edition, New York, p. 1064, QD5C5, 1961, C. 6. 

1. A METHOD OF IMPARTING A CHEMICAL WATERMARK OF SELECTED DESIGN TO A FINISHED SHEET OF PAPER WHICH COMPRISES THE STEPS OF PRINTING THE DESIGN ON A PORTION OF THE SURFACE OF SAID PAPER SHEET WITH A LIQUID COMPOSITION CONSISTING ESSENTIALLY OF A SYNTHETIC, THERMOSETTING, CURABLE RESIN AND AN ORGANIC SOLVENT, AND REMOVING SAID SOLVENT TO OBTAIN A SUBSTANTIALLY COLORLESS CHEMICAL WATERMARK OF SAID DEPOSITED RESIN HAVING AN INDEX OF REFRACTION OF ABOUT 1.4 TO ABOUT 1.7, AND SAID CHEMICAL WATERMARK BEING SUBSTANTIALLY FREE FROM GLOSS, HAVING INK RECEPTIVITY AND RESISTING DISCOLORATION WITH AGING SUBSTANTIALLY IN THE SAME WAY AS THE PAPER. 